What Moms-to-Be Should Know About Cervical Length

Cervical length measurements may help narrow down pregnancy due date window


The due date guessing game may be about to get a whole lot easier.

A new study from Thomas Jefferson University (TJU) in Philadelphia found that a routine test used to screen for preterm birth may also reveal whether at-term birth is likely within one week.

This finding could potentially help doctors narrow down a pregnant woman's due date window. Currently, only 5 percent of women deliver on their predicted due date, according to the American Academy of Pediatrics.

"Women always ask for a better sense of their delivery date in order to help them prepare for work leave, or to make contingency plans for sibling-care during labor," said senior study author Vincenzo Berghella, MD, in a press release. "These are plans which help reduce a woman's anxiety about the onset of labor. But having a better sense can also help obstetricians provide information that could help improve or even save a mother or baby's life."

Dr. Berghella is a professor of obstetrics and gynecology at TJU and the director of maternal fetal medicine at Thomas Jefferson University Hospital.

The test uses an ultrasound to measure a pregnant woman's cervix (the passageway at the entrance to the uterus that opens up to make way for a baby during delivery). Until now, this test has been considered the "gold standard" for detecting preterm birth risk — the shorter the cervix, the more likely labor is imminent.

Recently, a number of studies have looked at whether this test could also be used to predict at-term birth.

For this study, Dr. Berghella and team pooled data from five studies in which researchers used ultrasounds to measure cervical length in a total of 735 women with single-child pregnancies.

When the cervix measured more than 30 milimeters at a woman's due date, Dr. Berghella and team found that she had a less than a 50 percent chance of delivering within one week.

When a woman's cervix measured 10 milimeters or less at that time, however, she had more than an 85 percent chance of delivering within one week.

According to Dr. Berghella and team, cervical length is a good predictor of due date because it tracks the natural progress of a mother's body toward labor.

This study was published Oct. 28 in BJOG: An International Journal of Obstetrics and Gynaecology.

No funding sources or conflicts of interest were disclosed.